I know of a family who were well known to DOCS, both parents had mental issues due to drug use, etc. They went on to have a 3rd child and that baby was not taken from their care at birth. So my point is that if a family well known to DOCS wouldn't have a bub taken, it must be quite serious indeed for the removal of a 1st baby....how common? I don't know of anyone myself (thankfully) but I don't have that much contact with DOCS- well not on a regular basis.
Sometimes I suppose they can pre-determine that the parents don't have the mental capacity to safely care for a child (though in the case I just mentioned in my opinion it was obvious the parents we incapible - but they kept the child -until it was about 6 mths old anyway).

It's all so bl***y sad really. I remember my first time I had to report - I was a fresh director, I knew it was the right thing, didn't stop the tears when the children were seized that day, from my service.....just awful. And the worst part, we don't get follow up info on those children, they disappear into the system and you never hear of them again alot of the time.